Arc interrupting device



Sept. 19, 1961 D. w. COLLIER 3,001,050

ARC INTERRUPTING DEVICE Filed July 2, 1959 INVENTOR. Donald ZM CaZZa'er'BY/wd,

Patented Sept. 19, 1961 3,001,050 Anc INTERRUPTING DEVICE Donald W.Collier, Wayne, NJ., assignor to McGraw- This invention relates tocircuit .interrupting devices and more particularly to an arcextinguishing medium for a circuit interrupting device.

Upon the opening of a faulted circuit by certain types of overcurrentprotective devices, an arc may be struck at the break so that the faultcurrent is not interrupted until the arc is extinguished. This arccurrent is generally carried by electrons emitted from the partedconductors and positive ions formed as the result of collisions betweenthese emitted electrons and gas molecules in the arc path and also bythermal ionization due to the heat of the arc itself. The positive ionsplay an important role in maintaining the arc since it is theircollisions with the negative side of the break that maintains itstemperature and emission of electrons. -In the case of a fuse, thisionization is greatly enhanced by the metallic vapor formed between theparted ends of the fusible element as the fuse blows. In some electricalsystems it is imperative that this arc be rapidly extinguished so thatthe duration of the fault current is insuicient to result in damage tothe systems components.

It is the object of this invention to provide circuit iny terruptingdevice with an arc quenching medium which Vgaseous arc quenching mediumfor fuses which accomplishes arc extinction by capturing emittedelectrons and by combining chemically with the metalized vapor and endsof the parted fusible element to severely limit ionization.

Other objects and advantages of the invention will become apparent fromthe following detailed description of the invention taken in view of theaccompanying drawing which shows a fuse having a gaseous arcextinguishing medium according to the invention.

In general terms, the invention comprises providing a fuse with agaseous arc extinguishing medium 'containing perchloryl uoride,chemically symbolized C1031?. This gas accomplishes arc extinction intwo ways. First, it has a high electron aiiinity enabling it to captureelectrons emitted from the parted ends of the fusible element, therebypreventing these electrons from colliding with gas molecules in the arcpath to form positive ions necessary to sustain the arc current. Second,when subject to the heat of the arc, C1031: decomposes into an oxidizingagent which oxidizes the metallic vapor formed as the fuse blows, andalso oxidizes the ends of the parted element. The oxides thus formed arenon-conductive so that a non-conducting medium is interposed in the arcpath to severely reduce its current carrying ability. In addition, anyoxide formed in the break will increase the electrical resistance of thefusible element and thereby promote arc extinction.

Referring now to the drawing in greater detail, the circuit interruptingdevice shown therein, comprises a fuse 10 having a hollow casing 12 ofany suitable gas impervious insulating material, such as glass or thelike, and a pair of conductive end caps 14 and 16, disposed at each endof'casing 12 and secured thereto in a hermetically sealed relationshipby a suitable cementing compound 18. Casing' 12 and end caps '14 and 16deiine a hermetically sealed chamber 19. A fusible element 20 isdisposed coaxially within the housing and is electrically connected toeach of the conductive end caps .14 and 16 to complete the electricalcircuit through the fuse. A nipple 22 is provided in casing I12 so thatchamber 19 may charged with ClO3F.

In operation, when the fusible element 20 is subjected to a faultcurrent, it will begin to melt at some point along its length and thenseparate as the heated metal vaporizes. If the circuit voltage issuciently high, an arc will be struck at the break. As the arclengthens, due to evaporation of the material from the ends of thefusible element 20 a portion of the molecules of ClOF decompose to forma strong oxidizing agent which combines with the metallic vapor and theends of the fusible element to form non-conducting metallic oxides. Inaddition, the ClOaF molecules and any gases formed by this decompositioncapture emitted electrons, thus substantially limiting the freeelectrons available to form the positive ions necessary to sustain thearc. As a result of these actions, the arc will be extinguished.

I claim:

1. A circuit interrupting device having a container, a fusible elementdisposed within said container and adapted to be-connected in anelectrical circuit, and a gaseous arc extinguishing medium disposedwithin said container and including perchloryl fluoride.

2. A circuit interrupting device having a container, an arcextinguishing medium disposed within said container and includingperchloryl fluoride, and separable electrical conductive means disposedwithin said container for interrupting an electrical circuit whereby anarc will be struck between the separated portions thereof, said mediumelecting extinction of said arc.

3. A circuit interrupting device having a container, a gaseous arcextinguishing medium disposed within said container and includingperchloryl iiuoride, and means for striking an arc within saidcontainer, said medium effecting extinction of said arc.

References Cited in the tile of this patent UNITED STATES PATENTS2,221,720 Prince Nov. 12, 1940 2,539,261 Miller Jan. 23, 1951 FOREIGNPATENTS 303,090 Great Britain Dec. 28, 1928

1. A CIRCUIT INTERRUPTING DEVICE HAVING A CONTAINER, A FUSIBLE ELEMENTDISPOSED WITHIN SAID CONTAINER AND ADAPTED TO BE CONNECTED IN ANELECTRICAL CIRCUIT, AND A GASEOUS ARC EXTINGUISHING MEDIUM DISPOSEDWITHIN SAID CONTAINER AND INCLUDING PERCHLORYL FLUORIDE.